生物质与煤矸石混合燃烧特性分析

文章利用TG-DTA热重分析仪,对玉米秸秆、向日葵花盘和煤矸石进行混合燃烧试验,研究了混合试样的燃烧特性。结果表明:向日葵花盘较玉米秸秆更易燃烧,燃烧过程更为剧烈、发热量更高,燃烧特性更好,而玉米秸秆燃烧过程较为稳定;两种生物质与煤矸石混合燃烧过程中,向日葵花盘与煤矸石表现出的协同作用更明显;不同含量的向日葵花盘与煤矸石燃烧过程中,随着向日葵花盘含量的增加,着火温度呈现先升高后降低的趋势,最大失重温度呈现先降低后升高的趋势,最大失重率和总的失重率均增大;300℃之前混合试样的转化率相差不大,300～600℃时向日葵花盘含量越高转化率越大,600℃之后向日葵花盘含量越少转化率增加速度越快。     

烘焙对玉米秸秆碱金属释放动力学的影响

为研究烘焙对玉米秸秆碱金属释放动力学的影响,利用多点LIBS测量烘焙玉米秸秆燃烧过程中碱金属释放,并进行碱金属释放动力学模拟。结果表明,低温烘焙玉米秸秆燃烧时,在挥发分阶段释放至气相中的钾浓度高,在焦燃烧阶段钾释放浓度较低;高温烘焙玉米秸秆燃烧时,在挥发分阶段释放的钾浓度低,在焦燃烧阶段释放的钾浓度高。在挥发分阶段,碱金属释放动力学的活化能随烘焙温度升高,先升高后下降;在焦燃烧阶段,活化能随烘焙温度升高整体降低。     

LNK三元熔盐热裂解水稻秸秆的研究

在熔融LiCl-NaCl-KCl(LNK)三元氯化熔盐作用下进行水稻秸秆热裂解的研究,考察了熔盐、裂解温度对热裂解产物产率和气相组成的影响,分别用气质联用仪(GC-MS)和气相色谱分析了液相和气相产物组成。结果表明:在LNK熔盐作用下,液相产物、固相产物和CO2含量增加,气相产物和CH4含量降低;液相产物产率随温度升高先增加后降低,460℃时产率最高为14.15%;气相产物以CO2,CH4,H2和CO为主,CO2含量随温度升高逐渐降低,CH4和H2含量逐渐增加;液相产物中的有机化合物以酮类、酚类和醛类为主,酮类随温度升高先增加后降低,酚类在540℃时最高;高温有利于酮类化合物的生成。碱金属盐促进酮类的生成,对酚类有一定的抑制作用。研究为秸秆类生物质资源的能源化和高值化利用提供了一定的参考。     

分时收集条件下稻秸理化性状变化初步研究

以高茬(留茬高度50～60 cm)秸秆为对象,每间隔7 d采集秸秆样品一次,分析自然状态下留茬稻秸理化性状变化(含水率、热值及作物养分大、中微量元素含量等),同时记录气象资料(如雨日、雨量等),旨在为秸秆分时收集、秸秆热解或直燃能源化利用提供基础数据。结果表明,在温度较高、降雨较多季节,稻秸中钾、钙等营养元素被淋洗、秸秆灰分减少,含水率变化不大,热值、有机物质等损失较少,相关分析表明秸秆含水率与土壤含水量、空气湿度、风速等多重因素有关。初步结论:采用秸秆分时收集,可使秸秆中钾、钙等养分资源归还农田、降低秸秆灰分含量,且不影响秸秆热值。     

变废为宝:我国已提出秸秆资源“五料化”利用途径

<正>每年秋收之际,总有大量的小麦、玉米等秸秆在田间焚烧,不仅污染了环境,同时也造成了严重的资源浪费。实际上,秸秆是一种具有多用途的生物质资源,农作物光合作用的产物有一半以上存在于秸秆中,富含氮、磷、钾、钙、镁和有机质等。近年来,我国秸秆的综合利用率不断提升,2013年已经达到约76%。但与农业发达国家相比,仍有很大的进步空间。那么,秸秆的综合利用有哪些好处、技术方面需要哪些突破、如何进一步提升秸秆的综合利用率?对     

秸秆与神府烟煤掺烧结渣特性中试研究

在一台50 kW中试下行炉中,利用自主开发的在线检测系统研究了神府烟煤分别与不同比例水稻秸秆、小麦秸秆掺烧的结渣特性.结果表明:水稻与小麦秸秆的掺烧均会促进结渣.随着水稻秸秆掺烧比例的增加,最终稳定的灰渣厚度先增大后减小,稳定相对热流密度先减小后增大.小麦秸秆对结渣倾向的恶化程度与其掺烧比例呈正相关.灰渣初始层对换热面...     

电镀污泥焚烧后的灰渣分析

焚烧法是防止污泥中重金属污染的有效方法，电镀污泥焚烧处理后的灰渣中含有大量的重金属，需要对灰渣中的成分进行试验研究。对电镀污泥在管式炉内进行了不同焚烧温度和焚烧时间的试验后，将高温焚烧后的电镀污泥灰渣进行了X射线衍射（xRD）和能谱分析（EDX），得到了电镀污泥焚烧后的灰渣成分与焚烧温度和焚烧时间的关系。图5表1参8     

向日葵秸秆固体燃料成型参数多响应优化设计

采用三因素三水平响应面试验设计研究含水率、温度、压力对向日葵秸秆成型燃料物理特性(密度、耐久性、抗跌碎性)的影响规律,并应用马氏距离法对工艺参数进行三响应优化设计。结果表明:向日葵秸秆固体燃料密度与含水率成反比,与压力成正比,随温度升高呈先增后缓趋势。耐久性和抗跌碎性均随含水率升高而降低,随温度、压力的升高而升高。当含水率在5%～8%,温度在110～140℃,压力在100～120 MPa时可成型优质向日葵秸秆燃料。三响应优化参数组合为:含水率5.8%,温度128.8℃,压力114.0 MPa,此条件下燃料密度、耐久性、抗跌碎性分别达1.03 g/cm~3、98.75%、99.76%,此结果可为向日葵秸秆固体燃料的工业化制备提供理论参考。     

秸秆灰特性的研究

按照D1102-84灰分标准测定方法,对小麦、水稻、玉米、黄豆、高粱、棉花等几种秸秆样本进行了工业分析;在ZRC2000智能灰熔点测定仪上对不同秸秆进行了灰熔点测试;在不同的温度和停留时间下,在马弗炉上对不同秸秆进行了热灼烧试验.结果表明:秸秆挥发分含量较高,灰熔点比较低,无机碱金属析出量随着温度的升高和停留时间的增加而增加.     

应用计算机控制系统预防危险废物回转窑焚烧结渣的研究

危险废物回转窑焚烧处置工艺具有诸多优点,但是当危险废物焚烧产生的灰渣熔融温度较低时,窑内的高温气氛会将灰渣颗粒熔融成液相,导致回转窑的结渣。灰渣的熔融实验结果证明,灰渣的熔融温度比较低,变形温度仅有1000℃左右。化学组分对灰渣熔融温度的影响研究表明,SiO2、Al2O3、CaO和CaSO4都对灰渣的熔融温度起到了升高的作用。采用计算机控制系统对整个系统进行监测、控制和管理,控制回转窑的温度在略低于灰渣熔融温度的水平运行,或者对危险废物在焚烧前进行合理的预混配伍,都能起到较好的预防回转窑结渣的作用。     

Ash transformation and deposition characteristic during straw combustion

The main objective of this study was to determine ash transformation and deposition characteristic for three types of straw (corn straw, oat straw, and rice straw) combustion at temperatures between 500 and 1000°C. The collected deposits on the sampling probe were characterized with X-ray diffraction and scanning electron microscopy combined with energy dispersive X-ray analysis. The results indicated that the ash forming processes of straw were influenced by fuel composition and temperature. The quantity of corn straw ash collected from deposition probe was noticeably lower than that of oat straw and rice straw due to different contents of K, S, and Si in fuels. The deposition amounts of corn straw and oat straw followed a linear pattern at temperatures below 800°C, while rice straw followed a nonlinear pattern as a function of temperature. Corn straw was an ideal fuel compared to oat straw and rice straw from the points of deposition amounts and appearance. It also can be found that silicon, calcium, potassium, and sulfur were key points in the forming process of ash deposits.     

生物质与烟煤灰的理化特性及混合灰熔融特性研究

文章利用扫描电子显微镜(SEM)、X射线荧光光谱仪(XRF)、X射线荧光衍射仪(XRD)、灰熔融特性分析仪对4种生物质(海草、梨木、榛子壳、稻秆)灰与神木烟煤灰的混合灰的熔融特性进行了研究。研究发现:水生生物质(海草)灰的掺混使混合灰的熔融特性温度先升高再降低;两种木本生物质(梨木和榛子壳)灰的掺混使混合灰的熔融特性温度逐渐升高;草本生物质(稻秆)灰的掺混对混合灰熔融特性温度的影响与水生生物质灰类似。由XRF分析可知:Na2O和CaO对于混合灰的熔融特性温度有更明显的影响,随着混合灰中Na2O含量的逐渐增加,混合灰的熔融特性温度逐渐下降;随着混合灰中CaO含量的逐渐增加,混合灰的熔融特性温度逐渐上升。由XRD结果可知:水生生物质灰在高温下容易形成熔点较低的碱金属硅酸盐,使混合灰的熔点降低;木本生物质灰中的CaCO3含量较高,能够提高混合灰的熔点;草本生物质灰与水生生物质灰类似,含有的低熔点碱金属硅铝酸盐使混合灰的熔点降低。     

不同添加剂对生物质灰分及床料的熔融性影响

使用灰熔点法,分析Al2O3、高岭土、CaO对稻草、麦秸秆与河砂及煤灰混合物的熔融性质的影响,研究结果表明灰熔点法在预测添加剂对生物质灰分与床料熔融粘结改善方面具有较强的适用性。煤灰与两种生物质混合物的灰熔点要高于河砂与两种生物质灰分混合物的灰熔点,麦秸秆与床料混合后的灰熔点要高于相同奈件下稻草与床料混合后的灰熔点,三种添加剂对提高生物质灰与煤灰、河砂混合物的灰熔点结果从高到低依次是Al2O3,高岭土,CaO。     

不同生物质灰的理化特性

根据我国和美国国家标准,将稻草、松木屑和梧桐树叶3种生物质分别在815和600℃下制灰,此外也在500℃下制灰进行比较。测定了灰分量和灰成分,考察了灰成分中氧化物的含量变化以及生物质灰的积灰、结渣特性;利用X射线衍射方法和SEM对不同温度灰的物相和灰形态进行了分析;利用灰熔点仪测定了生物质灰的灰熔点。研究表明:灰分量、灰成分、物相变化、灰形态以及灰熔点均与灰化温度密切相关,600℃的灰化温度比较适合研究生物质灰分的性质。     

Promoting effect of biomass ash additives on high-temperature gasification of petroleum coke: Reactivity and kinetic analysis

The effect of biomass ash (rice straw ash (RSA) and cotton straw ash (CSA)) on the gasification reactivity and the evolution of physicochemical structure of petcoke char was investigated. The catalytic effect of CSA was significantly higher than that of RSA, and the catalytic effect of biomass ash was enhanced at lower gasification temperature and for higher blending ratio of biomass ash. The promoting effect of biomass ash was related to the increase of active AAEM content, the decrease of order degree of carbon structure and the development of surface structure in char gasification after biomass ash addition, which was more significant for CSA, at lower temperature and for higher blending ratio. Moreover, the shrinking core model was suitable for char gasification, and the additions of RSA and CSA reduced the activation energy of petcoke char gasification from 199.84 kJ mol⁻¹ to 159.85 kJ mol⁻¹ and 62.75 kJ mol⁻¹, respectively.     

The use of equilibrium thermodynamic models for the prediction of inorganic phase changes in the co-firing of wheat straw with El Cerrejon coal

The combustion of pulverised coal in power stations results in slagging and fouling in the boiler section and this can be a more severe problem when co-fired with biomass, especially straw. Prediction of the effects of different combination of biomass and coal are helpful to the plant operators. Predictive software gives information about the onset and nature of the slag formed but often the results of these calculations have to be validated. This was undertaken in this work which gave a comparison of ash behaviour for coal (El Cerrejon) and wheat straw blends studied by ash fusion test, X-ray diffraction (XRD) and by using predictive software (FactSage). Ash prepared in the laboratory was also compared with ash produced in a 250 kW pilot-scale test furnace. The FactSage model showed good agreements with XRD data for the presence of inorganic phases with temperature, although it predicted some inorganic phases which are not detected in the XRD, particularly in low temperature ashes. Nevertheless, FactSage gave insight into liquid phase formation, more so than the ash fusion test, since it predicted the beginning of slag formation below the initial deformation temperature seen in the ash fusion test. For the coal, wheat straw and their blends, FactSage always predicted that slag formation is near to completion by the flow temperature observed in the ash fusion test.     

The properties of pellets from mixing bamboo and rice straw

Rice straw pellets are the main type of biomass solid fuel and have great potential as a bioenergy resource of the future in China. But it also showed important problems because of its high content of ashes and its low gross calorific value, reducing the possibility to be used in domestic heating. It was certified that mixing different types of biomass materials was helpful to improve the properties of pellets. To improve properties of rice straw pellets and investigate the effect of mixing bamboo and rice straw on the pellet properties, some properties of pellets, manufactured using different mixing ratio of bamboo and rice straw particles, were determined in this research. It can be concluded from this research that physical properties of all pellets meet the requirements of Pellet Fuels Institute Standard Specification for Residential/Commercial Densified except for bulk density of pellets, manufactured using mixing ratio (≤3:2) of bamboo and rice straw. The inorganic ash and gross calorific value of rice straw pellets cannot meet the requirement of Pellet Fuels Institute Standard Specification for Residential/Commercial Densified (8.0%) and the minimum requirement for making commercial pellets of DIN 51731 (>17,500 J/g). Both properties are improved through mixing bamboo particles and rice straw particles. It is significant that inorganic ash content and gross calorific value of pellets, manufactured using mixing ratio (≥3:2) of bamboo and rice straw, were lower than 8.0% and higher than 17,500 J/g, respectively. This also shows that mixing different biomass materials is an effective way to optimize properties of biomass solid fuel. All pellets after improvement are proposed as biomass solid fuel and have the potential to be developed as commercial pellets on an industrial scale in China.     

Agglomeration characteristics of alumina sand-straw ash mixtures at elevated temperatures

The agglomeration characteristics of alumina sand-straw ash mixtures were investigated at various levels of ash content (0.0, 3.3, 27.8, and 43.5%) and temperature (620, 740, 850, and 1000°C) using scanning electron microscopy and energy dispersive X-ray analysis techniques. Agglomeration of alumina sand did not take place below the temperature of 850°C at all levels of ash content, but at the temperature of 850°C a weak bonding of particles was observed. However, at the temperature of 1000°C, the alumina particles agglomerated in the presence of straw ash at all levels of ash content as a layer of ash melt bonded the particles together. The temperature at which agglomeration occurred was within the range of the initial deformation (921°C) and softening (1054°C) temperatures of straw ash and the liquidus temperature of potash feldspar (990 ± 20°C). The softening of straw ash and the formation of low melting temperature eutectic (potash feldspar) are two possible mechanisms for the agglomeration of alumina sand.     

垃圾焚烧飞灰熔融固化炉开发与试验研究

介绍了5000kg/d垃圾焚烧飞灰熔融固化试验炉结构特点,分析研究了垃圾焚烧飞灰化学成分、灰熔点对熔融固化炉炉膛截面热负荷、容积热负荷值的选取以及炉内衬耐火材料抗碱浸蚀抗高温性能的影响因素.对试验装置炉内各点温度变化和随着温度水平提高,炉内阻力减少的原因进行了分析,对飞灰熔融物用722S分光光度计和IRIS1000等离子体发射光谱仪进行浸出毒性鉴别,结果显示检测值均低于浸出毒性鉴别标准.应用数值模拟方法对炉内的速度场、温度场和飞灰颗粒浓度分布进行了计算分析,指出采用单通道送风比双通道送风对飞灰熔融颗粒收集更有利.     

The physicochemical properties of different biomass ashes at different ashing temperature

There are no specific standards for biomass ash analysis in China, so the standards for coal ash analysis are usually used to determine the property of biomass ash. Three kinds of biomass including rice straw, pine sawdust and Chinese Parasol Tree leaf burned at 815 °C, 600 °C and 500 °C respectively corresponding to the temperature required in the standard of GB and ASTM. The ash content and composition were analyzed. Based on the ash composition results, the volatilization of alkali oxides in biomass ash and slagging/fouling problems related to biomass thermochemical conversion were investigated. The alkali metals were relatively more volatile with the increasing of ashing temperature. The crystalline phase composition and surface morphology characteristics of the ash particles were investigated by XRD and SEM analysis. The increasing ashing temperature resulted in the decreasing of the diffraction intensities of metal salts and the increasing of the diffraction intensities of silicon compound. Ash fusion temperatures were measured by 5E-AFII Ash Fusion Analyzer. The results indicated that the ash content, composition, crystalline phases composition, surface morphology and ash fusibility were all closely related to ashing temperatures. The analysis at 600 °C ashing temperature was regarded as the optimal for an exact determination of ash properties.